Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing ECU change needed

Also check if you have a small hole in the throttle butterfly.

IvorMog: I've tried a few cm throttle but that doesn't change anything. I also checked the throttle butterfly and there is a small hole.

Roger: The 16 amp fuse above the battery is not the 'keep awake' fuse - when removed I still have 12 volts on pin 1 in the connector.

Today's results:
- Fitted the new ICV and there was actually a small change in behaviour but nothing significant. Seems to be a mixture related problem. The manifold below the throttle butterfly looks wet witch fits well with the hot exhausts and missfiring.
- Disconnected the Air Flow Sensor and noticed a small change in behaviour.
- Took of the inlet tubing between the Air Flow Sensor and the throttle housing and it didn't stall but idle was very rough and the catalytic converter got very hot.
Next step is changing the AFS. Ordered a used one (Escort 1.8 16V -99) for less than £40...

Since the original ‘event’ do you still have 5v on your TP sensor connector?

Yes, 5.01v with the same instrument.

I don’t know but..... when you shorted 5v to ground you may have put +5v into the oxygens sensor’s reference ground signal pin. Could you have buggered the oxygen sensor?

I don’t know what symptoms a bad oxygen sensor would give on your car?


B72 is the oxygen sensor

I have no prior knowledge of oxygen sensors but after a quick 'googling' I understand that the sond itself passively generates voltages between 0.1 and 0.9. According to descriptions available on the net, a faulty sensor can generate both lean and rich mixture signal/voltage. Can't find anything regarding feeding current through it though... Perhaps I will end up having to replace it

Correction: Found that both Internal and External short circuits can cause sensor failure (Hella).
Could the 5v be enough to do that kind of damage...

Maybe….. if it has no reverse polarity protection.

If it is shot I guess the engine will run (try to run) super rich and that might account for your symptoms/stalling?

Another contender for poor starting might also be B132, the camshaft position sensor?

(B25 & B25 are the engine and intake temp sensors)

I might be wrong about this but I thought the Lambda sensor only kicked in after the engine reached a certain temperature or time so that the sensor had time to warm up.

Until that time the ECU controlled the engine in an open loop based on the mapping.

Then when the engine and sensor reach a certain temperature it goes into closed loop and the oxygen feedback tunes the mixture.

IF (the biggest word in the English Language) that is correct, I'm not sure a faulty Lambda sensor would have any effect at start up.

I will concentrate on sensors that are influencing mixture most, such as the AFS and the Lambda sond. Those could cause the extreme exhaust heat if they don't work properly and makes it impossible to run the engine for any length of time. After 10 to 15 seconds the catalytic converter gets really hot...
Thanks for your information Roger... possibly several sensors has been affected. I don't really mind doing this kind of work since my Morgan is a hobby anyway, but not being able to drive it is annoying

Bob: Interesting... If you're right and assuming the Lambda sond is ok I guess the AFS could be the main culprit. Even more exciting to see what effect the 'new' AFS could have. I must get the exhaust temp under control before I can analyse any other problems.

Thank you all

Another day... not completely wasted 🙂
Fitted a 'new' AFS but it didn't solve the problem. A slight change in behaviour though. Easier to keep the engine alive and firing sounds a bit 'cleaner'.
After a discussion with one of the few Morgan garages here in Sweden I checked the catalytic converter for clogging but it looked fine.
Next I measured the lambdasond voltages but couldn't find the correct values. Mostly way to low which could indicate malfunction and a reason for too rich mixture.
Next step will be a not so new but checked (ok) lambdasond.
All-in-all I think I'm moving in the right direction.